Ore conditioning process



Oct. 16, E Bui-LER ET AL 1,977,262

ORE CONDI'IIONING PROCESS Filed April 25, 1950 Smil NSMASP atten/4,94

www SQ@ Patented Get. 16, 1934 can coNnirroNrNc raocrss Emmett Butler and Arthur K. Knickerbocker, St. Paul, and Richard 0. `izioelsing, Nashwauk, Minn.; Francis D. Butler special administrator of said Arthur K. Knickerbocker, deceased Application April 23, 1930, Serial No. lM6598 3 Claims.

The invention relates to the conditioning of ore and more particularly has reference to a process for mechanically separating the ore from the gangue. Y

A large proportion of all ore mined contains such a percentage of impurities as to make it unavailable for immediate commercial use. As a result of this condition the art of mineral separation or concentration has, within the last nity years, been highly developed. At the present time, ore which was heretofore commercially unavailable,` may now be used as a result of special treatment. However, the fact nevertheless remains that a considerable amount of ore F of many minerals is wasted because of the lack of an adequate process for the removal of the impurities contained therein. Particularly is this true of iron ore which frequently contains high percentages of silica.

Within recent years developments in the ore separation art have been directed to improvements of separate process steps and apparatus for carrying out the same so that the maximum yield of concentrates having low proportions of impurities may be obtained from crude ore. Up to the present it appears that renements of this nature have reached their ultimate limit. Still the concentrates obtained are not up to the desired standard as they contain high percentages of undesirable constituents as impurities. The reason for this condition may be found in the economic theory of intensive utilization. Further ccnditioning of the concentrates so as to reduce the proportion `of impurities contained r' therein, while often being feasible on paper have proved to be impractical in actual practice because they exceed the limit of economical production conditions.

The major object of this invention is the provision of a conditioning process for ore to produce a maximum yield of merchantable concentrates.

An equally important object of the invention is the provision of an oreconcentrating method .wherein low grade ore may be conditioned so as to remove the maximum amount of Vimpurities therefrom.

Another object of the invention is the provision of a process for conditioning ore inwhich the oversize from a sizing stage is jigged so as to concentrate the same.

Another object of the invention is to devise an. ore conditioning process wherein the nes fromJ the sizing stage are Washed and classified, and

the concentrates from the classifying stage sub-l jected to a second washing stage, to produce concentrates for use as a commercial product.

Still another object is the provision of an ore concentrating -process whereby the fines fromal sizing stage are treated in a log washer, the overflow therefrom being classied and the concentrates from the classier and log washer being treated in a second washing stage to produce concentrates ready for commercial use.

Yet another object of the invention is the provision of an ore concentrating method in which the crude ore is suitably sized, thefoversize therefrom subjected to a jigging stage, theiines from the sizing stage Washed and classified, and the concentrates from the washing stage and the classifying stage subjected to a second Washing stage to produce concentrates ready for commercial use.

Still a further object of the invention is the conditioning of ore comprising subjecting the ore toa sizing stage, passing the oversize therefrom to a jigging stage, crushing the tailings from the jigging stage and magnetically separating the concentrate therefrom and sintering the same. n

Yet a further object of the invention is to devise an ore separation method wherein theV ore' is subjected to a sizing stage, the nes therefrom Washed and classified, the concentrates from the classifying stage subjected to a second washing stage, the tailings from the second washing stage subjected to magnetic separation so as to remove the ore therefrom Vand then sintering the ore.

With these and other objects in view, the invention consists in the method and apparatus to be hereinafter set forth and claimed with the understanding that the several apparatus features disclosed and the various steps and stages of the process set forth in the procedure may be L widely varied without departing from the spirit of the invention or the scope of the appended claims. I i

The invention comprehends the provision of an ore concentrating or separating process wherein a great amount of impurities are removed from the ore so that a low grade ore may be converted into a merchantable form. One method of practically effecting the concept of the invention is the provision of a sizing stage wherein the ore may be suitably sized, the oversize being subjected to a jigging treatment. The fines from thev sizing stage may be washed and classied and the concentrates from the washing and/orv classifying stage subjected to a second washing t bV stage so that the resulting concentrates therefrom will be ready for commercial use. The invention further comprehends the treatment of the tailings from the jigging stage and the second washing stage so that they may be made available.

In order to makev the invention more clearly understood there is shown in the accompanying drawing a diagrammatic representation for carrying the same into practical ciect. It is to be understood that the various steps of the process are not to be limited to the forms shown in the drawing, which for the purpose of vexplanation have been made the subject of illustration. Y l

In the drawing:

The figure is a diagrammatic view of a plant layout for carrying out the process forming the subject-matter of this application.

In the drawing there is shown a layout or flow sheet for an ore conditioning plant in which the crude ore is rst introduced into a grizzly 1 at the head of the plant. Ore of plus 5" in size is deposited in a rock car while the undersize drops into the pocket of the grizzly, and is thence conveyed by a belt conveyor to a trommel 2 which has associated therewith a rock screen 3. Other types of sizing apparatus'than a trommel may be employed under certain circumstances.

y Before entering the trommel the ore may be weighed by means of a weightometer 4. While av weightometer of the Merrick type has been shown, it is to be understood that any other suitable type of weightometer may be employed if desired.

I'he trommel 2`is provided` with 1"V openings through which the lines of the crude'orepass directly to a second trommel 5. As stated in connection with trommel 2, other sizing apparatus may be employed in lieu of trommel 5. The oversize passes to the rock screen 3, provided with Bg openings so that'only ore under that size may pass therethrough.V Ore passing through the mesh of the screen is led to a crusher 6 of the Symons type although any other crusher desired may be employed. Crushed ore from the crusher 6 is led to the second trommel 5 Where it is mixed with the nes from the trommel 2. As indicated in the drawing, oversize from the screen 3 associated with the trommel 2 isconducted in any convenient mannerto a rock hopper 7. a. i;

y'Ihe grizzly and the trommels 2 and 5, it will'be appreciated serve to size the ore preparatory to subsequent treatment to be hereinafter described. It is to be understood, however, that a procedure other than herein set forth may be employed for sizing. v

` The 20 foot trommel 5 is provided with 1/2" openings although it is to be understood that the invention is not limited to a trommel of this length having openings of this size. For example, if desired 3/3 openings in the trommel may be used and other trommel lengths employed.

It will be appreciated that in the sizing stage described the ore is progressively reduced in size by separation in the machines or apparatus mentioned.

Fines or undersize from the trommel 5 are transported in any convenient manner to a log washer 8 of any suitable type. The log washer may have either a single log or a plurality of logs formed either of wood or metal. At its overow end the log washer is provided with an overilow line .in which the sands and other similar materials of the log washer are conducted to a Dorr.

bowl classiiier 9 or any other classier. In the Dorr bowl classifier the ore is further treated and the tailings therefrom are conducted to a tailings pond as indicated or to further treatment.

The concentrates from the log washer and the Dorr bowl classiiier are usually collected in a concentrate bin 11 after which they are ready for shipment and commercial rening. It is also the custom to mix with these concentrates the oversize from thetrommel 5. Instead of employing this practice, however, the invention contemplates further treatment of the concentrates and the oversize just mentioned, so as to remove from them further amounts of impurities, which in the case of iron are principally silica.

Table I, which is compiled from data obtained at the Harrison washing plant of Cooley, Minnesota, in the Mesaba iron range, shows an analysis of these concentrates and the oversize. With reference to this table the desirability of further conditioning the ore so that a better commercial product may be obtained is at once appreciated. This'table is as follows:

TABLE I While the ore contains other substances such as oxygen, alumina, magnesia, phosphorus, carbon dioxide, sulphur and water, iron and silica are by far the principal constituents. Hence reference is made'only to the iron and silica content. Itis to be noted that two analyses are given for the ore at the different stages of treatment listed. These refer to the maximum and minimum value of the iron and silica content of the ore. Each value given in the heading Tonnage percentage shows the percentage of ther total tonnage of 'crude ore placed in the grizzly at the head of the plant at the particular stage of treatment. For the sake of simplicity consider one hundred tons of crude ore deposited in the grizzly. Ten tons or 10% of the total is removed as rock. Of this 90 tons remaining, 58.5 tons leave the second trommel as fines and 31.5 tonsy leave as oversize.

From the foregoing table the desirability of further separating the silica from the ore soas to obtain a better commercial product is at once apparent. In order to carry this out the oversize from the trommel 5 and the concentrates from the log washer and the Dorr bowl classifier are subjected to separate treatments and the concentrates from these steps are nally combined in the concentrate bin 11.

Asan example, the oversizes from the trommel 5 may be subjected to a jigging step although it is to be understood that if the grade warrants it is sometimes desirable to ship these oversizes direct. rIhe oversize from the trommel 5 is conducted to a sizing screen 12 or other appropriate sizing apparatus, located at the head of the jigging plant. The fines from this sizing screen of less than /g" are directed to a battery of jigs 13 which may be of the McLanahan type while the oversizes from the screen are conducted to similar jigs 14. As is well known the McLa-nahan jig is of the piston type and is usually provided with four sieves mounted in one tank. While McLanahan jigs have been disclosed in connection with the process it is to be understood that other jigs may be employed if desired. Although the Mc- Lanahan jig employs water as a working fluid, it will be appreciated that the use of an air jig would not exceed the spirit of the invention nor depart from the scope of the appended claims.

Tailings from the jigs indicated by 13 and 14 are combined together and are conducted in any desirable manner to a shipping bin or stock pile. The concentrates of the jigs, on the other hand, are sent to the concentrate bin 11 and if desired may be mixed with the concentrates returned from a second washing stage, which will bel presently described.

In order to reduce the silica content of the log' washer and Dorr vbowl concentrates a second washing step is employed. As represented in the drawing, concentrates from the washer 8 and the classifier 9 may pass as indicated by lines 16 and 17 respectively to a second washing stage employing a battery of washing. machines of the Rheolaveur type generally designated by the numeral 10.

As is well known the Rheolaveur washing machines are of the shallow pocket launder type classier, the operation of which depends upon the stratification of the crude material by reason of different specific gravities, in the different rate A of movement along the trough of the launder and in the different settling velocity of the diierent materials. When a mixture of particles is rst introduced into troughs, such as those shown, stratification occurs, the heavier materials settling to the bottom and moving at a less rapid rate than the upper materials. Suitable discharge slots are provided, and when reached the heavier material at the bottom of the trough is deposited therein while the lighter material continues along the trough. A suitable rewash line 15 is provided so thatthe material receivedin the last launder of the plant may be taken to the head launder and rewashed if desired. The concentrates in this instance, iron ore, are taken off and deposited in a concentrate bin 1l. Tailings or the lighter substance contained in the ore, such as the silica are deposited in a tailings pond.

While the concentrates from the log washer and the Dorr bowl classifier have been indicated as passing to the Rheolaveur plant, it is to be understood that the concentrates from either of these stages may be sent directly through line 18 to the concentrate bin if desired. In some instances it may be desirable to send the concentrates of the log washer to the bin 11 and the concentrates from the Dorr bowl classifier to the Rheolaveur machines. On the other hand it may be desirable to direct the log washer concentrates to the Rheolaveur plant and the classiiier concentrates to the collecting bin. Likewise it should be understood that the concentrates from the log washer, may if desired, be conducted through line 19 as indicated on the drawing, to the sizing screen 12 and thence to the jigs 13 and 14.

It has been stated that one of the objects of the invention is the conditioning of the tailings from the jigs and from the Rheolaveur machines. From an inspection of Table II, which is compiled from data obtained from the same source as that disclosed in Table"I,it may be observed that the quantity or mass of'these tailings represent a relatively large percentage of the ytotal tonnage. Table II is as follows:

v TABLE II y l Analysis of tailings at the H artisan washing plant (Note: The values given in connection with Table IIare composed in a manner similar to that employed in'connection with Table I.)

Instead of discarding and wasting these rejects,"

of the jigging and the Rheolaveur washing stage, the present invention contemplates further processing so as to obtain a merchantable product. This is accomplished by first crushing these tailings so as to liberate` the mineral from the silica. The size of the crushed material should bewithin that required for the proper separationof iron and silica and treatment'of material by a cylindrical rotating kiln. This type of kiln or any other suitable type desired may be employed. vIn the kiln the, material is preheated so as to drive oil all of the moisture contained therein and itsv temperature is raised to approximately that required for roasting.

After suitable heattreatment in the' drie`ra`s r described, the ore is passed to a roasterwhereit is subjected to a temperature of from SOW-'700 C.. in a reducing atmosphere. Iron ore in its crude state is of a composition corresponding tofleOvs. Roasting in, this manner reduces this compound to Fe304 which is known as magnetic oxide of iron. This reduction of the vore from its -ferrie form to the form of magnetite renders it sus- 1?@ ceptible of being magneticallyvsveparated from the other constituents of the material inthe roaster. If found necessary reducing agents can be employedto facilitate the reduction of the ferrie oxide to magnetite.

Ore thus roasted and converted may be classied into two sizes and then concentrated by means of magnetic cobbers and/or magnetic log Washers. The rst of these machines mentioned, namely, y the magnetic cobbers, are adapted to concentrate the large size which is substantially over 100 mesh while the magnetic log washers concentrate the small size of less than 100 mesh. It will be appreciated that the tailings from the magnetic concentrating machines will be extremely low in iron content and may economically be passed to waste.

If desired the tailings from the grizzly, the

screen 3, the log washer 8, and the Dorr bowly TABLE III Total concentrateanalysis of the Harrison washing plant Percentage composition ci zgajor constituents Tonnage 0 9 0r6 Treatment of concentrates percentage non' silica e Not jigged or Rheo'd 50.00 55.51 14.30 53.85 l7.03 .Tigged and Rheod 39. 95 58. 42 10. 23 56. 95 12. oo

In both sets of values given in Table III the log washer concentrates were neither jigged nor subjected to the second washing stage, but vwere mixed directlywith the total jigandl the total Rheolaveur concentrates. Howeverthese figures will adequately show the advantageous. effects of employing the jigging step andthe second washing step. It may be observed that when the two imaximum values of the iron percentages are compared there will be found an increase in the iron content of substantially 3% when the jigging and second washing step are employed while the silica values associated with. those of the iron show a decrease in the silica content of l over 4%."

The same holds true for thesets of minimum: values where the increas'euin the iron content is substantially 3% and the decrease in the silica content is over 5%. v. y Y

It will be appreciated that when the tailings from the second washing step and from the-jigs are treated as herein set forth to convert the same into magnetic ironvoxidey end then separate .the magnetic iron oxide from the bulkv ofthe material, the efficiency of the process can be greatly improved. `l

While in disclosing the foregoing process and its modications, reference has been made to a specic crude ore and to specific concentrations. or ironand silica inthe ore, itis to be clearly understood that iron ore containing a varying iron In lieu of magnetic treatment, there mightand silica content maybe 'treated to advantage inaccordance vwith the lpresent invention. Ores containingV other Aconstituents may be advantageouslyy treated by the processing described..I It isl also to be understood that while in describing the operation of the present invention, reference has been made to specic types of concentrating, washing, crushingand other ore conditioning apparatusv and tospecific-sizes of the ore conditioned, that other machines susceptible of carryingout the several 'steps as herein set forth may be employed to advantage. Likewise, the ore undergoing treatment may be conditioned as to sizes other than those herein set forth.

While, there has been shown and described the preferred embodiment of my invention, it is to be understood that the invention is not confined to the precise details of construction herein set forth, by way of illustration, as it is apparent that many changes and variations may be made there,- in by'` those :skilled in the art without departing from the spirit of the invention, or exceeding thescope ofthe appended claims;

We claim: v l. A process for conditioningiron ore, comprising'progressivelysizing theore into decreasing sizes, further sizing the oversizedlast obtained and. jigging in separate lots the products of the last mentioned sizing, passing the undersized oft-herst mentioned sizing to a log washer, treatingthe-overfiow from the Washer in a bowl classifier, passing theconcentrates from the washer and classi'er to a launder type classier, and collecting the concentrates of the last mentioned classiiierand the'jigging.v

2. Aprocess -forconditioning iron ore, comprising progressively `sizing"the ore into decreasing sizes, treating the fines last obtained from said sizing in a log washer, combining the washer concentrates and the last over-size from the sizing, sizing such combined material and jigging the resulting'sizes separately, and passing the tails from the log washer to 'a bowl classifier.

3. A vprocess for .conditioning iron ore, comprising progressively sizing the ore into decreasing sizes, treating the fines last obtained from said sizing in a log-washer, combining the washer oonce'ntrates and the'last oversize from the sizing; sizing such combined material and jigging the resulting sizes separately','passing the tailings from' the logwashe to a bowl classifier; and subjecting the concentrates from such bowl classier to treatment in a'laun'der type classier.

' g EMMET'I BUTLER. f -ARTHUIFLA K. KNICKERBOCKER. RICHARD O. HOCKING. i.

ist) 

